This is the kind of thing that’s expected of a +3C world, although the idea of it being a threshold phenomenon is a bit unrealistic. So, it’s expected that these sinks might, overall, start releasing their sequestered Carbon, one here one year, another there another year. But if the biggest sinks start releasing theirs first, well, this is one of the Climate Surprises the IPCC and the U.S. National Climate Change assessment talk about. And they are not at all good.
Back in 2005, and again in 2010, the vast Amazon rainforest, which has been aptly described as the world’s lungs, briefly lost its ability to take in atmospheric carbon dioxide. Its drought-stressed trees were not growing and respiring enough to, on balance, draw carbon out of the air. Fires roared through the forest, transforming trees into kindling and releasing the carbon stored in their wood back into the air.
These episodes were the first times that the Amazon was documented to have lost its ability to take in atmospheric carbon on a net basis. The rainforest had become what’s called carbon-neutral. In other words, it released as much carbon as it took in. Scientists saw this as kind of a big deal.
This summer, a similar switch-off appears to be happening again in the Amazon. A severe drought is again stressing trees even as it is fanning…
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ecoquant
667 per centimeter : climate science, quantitative biology, statistics, and energy policy 
Yes, but there is a question of Carbon budget. The accounting for CO2 sources is pretty good. If there’s an excess coming into atmosphere not accounted for by ocean outgassing, or known land/biosphere emissions, or fossil fuels, or boosted northern forest growth (and decay), or permafrost melt, then it’s necessary to look for it. Moreover, it is possible to both discriminate between these sources by isotopic signature and close (airborne) monitoring.
One year does not a pattern make